EC7 pile design - TC250/SC7 Evolution Group 7 - FPS/AGS Mirror Group. Meeting 10am Tuesday 20th December 2011

Transcription

1 EC7 pile design - TC250/SC7 Evolution Group 7 - FPS/AGS Mirror Group Meeting 10am Tuesday 20th December 2011

2 TC250/SC7 Evolution Group 7 EC Mandate M/466 EN 19th May 2010 New Eurocodes Further Development of existing Eurocodes: Assess existing Eurocodes to reduce the number of Nationally determined parameters Simplify rules where relevant for limited and well identified field of application

3 TC250/SC7 Evolution Group 7 Members: AB, Christian Moormann (Germany) Panicos Papadopoulos (Cyprus) Arne Schram Simonsen (Norway) Chris Raison (UK) Sébastien Burlon and Roger Frank (France) Gary Axelsson (Sweden) Boleslaw Klosinski and Kazimierz Gwizdala (Poland) Alessandro Mandolini (Italy) Jan Kos (Czech Republic) Vassilios Papadopoulos (Greece) Leoncio Prieto (Spain)

4 EG7 FPS/AGS Mirror Group Members: Bob Handley Aarsleff Piling David Preece Bachy Soletanche Ltd Tony Suckling Balfour Beatty Ground Engineering Mark Pennington Balfour Beatty Ground Engineering David Beadman Byrne Looby Alan Willoner Carillion Dimitrios Selemetas Cementation Skanska Derek Egan Keller Foundations In the Loop Andrew Bond Chairman TC250/SC7 (Eurocode 7 committee) Brian Simpson Arup Dianne Jennings Federation of Piling Specialists

5 Geotechnical Design to EC7 Section Limit states to be verified by: Calculation Prescriptive Methods Experimental Models and Load Tests Observational Method

6 Section 2.4 Design By Calculation Actions Ground Properties Geometrical Data Characteristic Parameters Design Values (Partial Factors) Ultimate Limit States (ULS) Design Approach 1, 2 and 3 Serviceability Limit States (SLS)

7 Limit States EQU Equilibrium STR Failure in the Structure GEO Failure in the ground UPL Uplift HYD Hydraulic heave STR & GEO most relevant to pile foundations

8 Section Design Approach DA1 Original proposal with two sets of calculations Action & Material Factors Exception for pile design and ground anchorages DA2 Apply to resistances as an alternative to soil strength Single calculation DA3 Single calculation

9 Section Design Approach DA1 Two Calculations: 1 A1 + M1 + R1 2 A2 + M2/M1 + R4 (Use M1 for calculating resistance) (Use M2 for unfavourable actions such as NSF) DA2 Single Calculation: A1 + M1 + R2 DA3 Single Calculation: A1/A2 + M2 + R3 (A1 structural or A2 geotechnical actions)

10 Section 7 - Pile Foundations

11 Section 7.2 Limit States EQU Equilibrium STR Failure in the Structure GEO Failure in the ground UPL Uplift HYD Hydraulic heave STR & GEO most relevant to pile foundations Section lists a significant number of options

12 Section 7.3 Actions Axial Loads Compression and tension Transverse Loads Ground Displacement Negative Shaft Friction Ground heave Lateral Soil Movement (eg. Slopes or Abutment Loads)

13 Section 7.4 Design methods Static Load Tests Empirical Methods Calculation Dynamic Load Tests Observed performance

14 Section Compressive Ground Resistance Static Load Tests Ground Test Results [includes alternative calculation method] Dynamic Impact Tests Pile Driving Formulae Wave Equation Analysis Why not include calculation (from insitu and laboratory test results) as a separate option?

15 Section Tensile Ground Resistance Static Load Tests Ground Test Results [includes alternative calculation method] Why not include calculation (from insitu and laboratory test results) as a separate option?

16 Section 7.7 Transversely Loaded Piles Load Tests Ground Test Results Includes beam on springs type of analysis ALP or WALLAP Here the calculation method appears to be more acceptable

17 Section 7.8 Structural Design of Piles Interface with EC2 and EC3 Is EC2 a Problem? Should EC7 include rules rather than EC2?

18 UK National Annex to BS EN :2004

19 Section Design Approach DA1 Two Calculations: 1 A1 + M1 + R1 2 A2 + M2/M1 + R4 (Use M1 for calculating resistance) (Use M2 for unfavourable actions such as NSF) DA2 Single Calculation: A1 + M1 + R2 DA3 Single Calculation: A1/A2 + M2 + R3 (A1 structural or A2 geotechnical actions)

20 Section Design Approach (13) (4) Based on Bond (2010) - Note that the slide is not completely accurate. Norway Should be included in DA2 not DA3. France is just DA2

21 Partial Factors on Actions or the Effect of Actions Permanent Variable Action EC7 Factor Set UK NA Factor Set A1 A2 A1 A2 Unfavourable Favourable Unfavourable Favourable Main differences relate to: 1. Use of combination factors for actions that can exist simultaneously. 2. Factors for bridges are more extensive. 3. Basic factors for buildings remain unchanged.

22 Partial Factors on Soil Parameters Action EC7 Factor Set UK NA Factor Set M1 M2 M1 M2 Friction Angle tan φ Effective Cohesion c Undrained Shear Strength Cu Unconfined Strength UCS Unit Weight γ Only difference relates to unit weight; other factors remain unchanged.

23 Partial Resistance Factors for Driven Piles Action EC7 Factor Set UK NA Factor Set R1 R2 R3 R4 R1 R4 (No SLS) R4 (SLS) Base Shaft Total Tension Main differences for resistance factors relate to: 1. Factor set R4 where different values depend on whether SLS behaviour is verified or not (test or calculation). 2. Model factor to be applied to ground properties to derive characteristic values. 3. Model factor 1.4, but can be reduced to 1.2 if a load test is completed to calculated unfactored ultimate resistance. 4. Factor set R2 used for Design Approach 2 (not adopted by the UK). 5. Factor set R3 used for Design Approach 3 (not adopted by the UK).

24 Partial Resistance Factors for Bored Piles Action EC7 Factor Set UK NA Factor Set R1 R2 R3 R4 R1 R4 (No SLS) R4 (SLS) Base Shaft Total Tension Main differences for resistance factors relate to: 1. Factor set R4 where different values depend on whether SLS behaviour is verified or not (test or calculation). 2. Factor set R1 adopted for UK (Presumably to cater for additional model factor). 3. Model factor to be applied to ground properties to derive characteristic values. 4. Model factor 1.4, but can be reduced to 1.2 if a load test is completed to calculated unfactored ultimate resistance. 5. Factor set R2 used for Design Approach 2 (not adopted by the UK). 6. Factor set R3 used for Design Approach 3 (not adopted by the UK).

25 Partial Resistance Factors for Cfa Piles Action EC7 Factor Set UK NA Factor Set R1 R2 R3 R4 R1 R4 (No SLS) R4 (SLS) Base Shaft Total Tension Main differences for resistance factors relate to: 1. Factor set R4 where different values depend on whether SLS behaviour is verified or not (test or calculation). 2. Factor set R1 adopted for UK (Presumably to cater for additional model factor). 3. Model factor to be applied to ground properties to derive characteristic values. 4. Model factor 1.4, but can be reduced to 1.2 if a load test is completed to calculated unfactored ultimate resistance. 5. Factor set R2 used for Design Approach 2 (not adopted by the UK). 6. Factor set R3 used for Design Approach 3 (not adopted by the UK).

26 Example Bearing Capacity No SLS Check

27 Example Bearing Capacity SLS Check

28 Example Bearing Capacity ULS & SLS Check

29 Discussion & Feedback 1 How is EC7 Pile Design Actually Done? Is the UK Fixed on DA1 for Pile Design? Two Combinations to Consider Strength Factors or Resistance Factors? Compatibility with Structural Design Should EC7 be Revised to Include the NA Factors? Is Design by Calculation Already Covered by ?

30 Discussion & Feedback 2 Where Are the Problems? Are the Model Factors Correct? Are the Partial Factors Acceptable? Are Designs Compatible with BS 8004? How is Negative Shaft Friction Included? How is Ground Heave Included? Is There a Better Way?

31 Discussion & Feedback 3 Transverse Loading? Resistance Factor or Factors on Strength? SLS or ULS? Horizontal Loads from the Ground? Piled Retaining Walls Include Some Detail in Piling Section? Any Particular Issues? Structural Design Problems with EC2 or Not? Should EC7 Include Structural Design?

32 Discussion & Feedback 4 Other Limit States EQU, UPL and HYD Importance for Pile Design UPL and Resistance Informative Appendices Too Much Guidance? Include Pile Design? Other Issues